Penicillin G is a member of the penicillin family of antibiotics, effective against a range of infectious bacteria. This medication may be known by brand names like Pfizerpen® and is kept in stock in many hospital formularies, as well as consumer pharmacies. If a patient needs to take this medication, a doctor will determine an appropriate format and dosage and write a prescription. People must use care when taking this and other antibiotics to avoid developing drug resistance.

This medication interferes with cell wall synthesis, making it impossible for bacteria to survive. It is commonly given in the form of an injection, usually with a slow infusion to allow the medication to circulate through the body at an even rate. As the penicillin G comes into contact with bacteria, their rate of replication will start to slow and eventually they will die off.

Patients on penicillin G may have side effects like intestinal upset and headaches. Sometimes, people experience skin rashes, especially around the injection site. Patients who notice rapid swelling, heat, and other signs of inflammation at the location of the injection should tell their doctors. These may indicate an allergic response, or contamination of the injection. Rarely, patients can experience allergic responses where their airways close and they have difficulty breathing as a result of an extreme reaction to penicillin G.

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A doctor can prescribe this medication when she strongly suspects bacterial infection in many cases, although in others, it may be necessary to confirm the infection and run a culture to learn what organism is causing the problem, and whether it is susceptible to antibiotics. Doctors try to avoid using penicillin G and other antibiotics unless they absolutely need to, as bacteria can build up resistance with repeat exposure, making it harder to treat serious infections. Using antibiotics when they are not necessary can expose people to the risk of resistant infections in the future.

While on penicillin G, patients should note any side effects, and should report continuing symptoms if the original infection does not appear to respond to treatment. It is possible the infection is not caused by bacteria, or that the bacteria are resistant to penicillin G. The doctor can run some more tests to find a more appropriate course of therapy. People with a history of adverse reactions to any member of the penicillin family should make sure their doctors are aware, as the doctor may need to choose a different medication to treat infection.

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